Mattress



FIG. 1 is a top, front and side perspective view showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a front elevational view thereof;

FIG. 6 is a rear elevational view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a top, front and side perspective view showing an environmental usage.

The broken line depictions of a person are illustrative of environmental structure and form no part of the claimed design. 

The ornamental design for a mattress, as shown and described. 